This invention relates to document feeders and more particularly to an envelope feeder used to transport documents from an envelope tray or hopper to a document processing location. This invention is related to co-pending application Ser. No. 650,926 filed Sept. 14, 1984, entitled Demand Document Feeder and assigned to the same assignee as this application (hereinafter the '926 application).
There are many instances of applications which require envelopes in a stack to be transported from a hopper to an envelope reading station or to envelope processing equipment. The '926 application illustrates one such example where envelopes are transported from the hopper to an envelope reading position where the operator reads the zip code and keys it into a computer by means of a keyboard. The operator then advances the envelope to a zip code printing station where a bar code is printed on the envelope which corresponds to the zip code entered by the operator. The '926 application illustrates an improved demand document feeder for accomplishing the feeding of the envelopes from the hopper to the reading position.
A problem with the device shown in the '926 application is its difficulty in feeding thick, rigid or heavy envelopes as they tend to push the lower driven roller of the first set of feed rollers away from the driving roller. The envelope is not bent around the driving roller a sufficient amount to force the envelope into the nip. The force from the drive roller applied through the envelope to the driven roller is insufficient to overcome the brake force applied to the driven roller. The brake is used to separate two or more confronting documents such that only one document is fed through the nip at a time. With the driving roller rotating, and the envelope not being forced into the nip, the heavy envelope merely pushes the driven roller away from the drive roller without being fed into the nip so that a stalled condition is present.
Applicant's invention overcomes the problem of the feeder illustrated in the '926 application. By changing the angle at which the documents are fed, and providing a uniquely designed spring and roller assembly, applicant has devised a means to feed documents regardless of their thickness, rigidity or weight. A drive roller is driven by a motor through a one-way clutch. The driven roller has a brake mechanism which retards its rotation. The force applied by the drive roller is sufficient to overcome the brake force so that the driven roller will rotate in an envelope feed direction when it contacts the drive roller. Just as in the '926 application, when a single envelope is in the nip, the force from the drive roller will overcome the brake force applied to the driven roller causing the envelope to be fed through the nip. In the improved design disclosed herein, the envelopes are fed in a nearly straight-through path with the envelope only being slightly bent around the drive roller.
The braking force minimizes the possibility of two documents being fed through the nip at the same time by stopping the second envelope until the first envelope clears the nip. Just as in the '926 application, there is a second set of drive and driven rollers positioned downstream of the first set to give added assurance of feeding only one envelope at a time and to hold the envelope with a portion of it extending into the document reading position.
There is an inverted "U" shaped spring with one arm of the "U" shaped spring mounted to the feeder frame. The other end of the "U" shaped spring is mounted to the shaft of the driven roller. The design of the spring causes the driven roller to quickly oscillate when there is no document in the nip. This oscillation causes the stack of documents to be lightly pulled aiding in the envelope feeding. When an envelope enters the nip, the oscillation immediately stops and the driven roller separates from the drive roller by means of the "U" shaped spring. The force from the drive roller is transmitted through the document to the driven roller just as in the prior design feeder. However, with the uniquely designed "U" shaped spring, thick documents will still enter the nip a sufficient amount to cause the force from the drive roller to be transmitted through the document to the driven roller without stalling. As soon as a document clears the nip, the oscillation begins again.
There is a second set of drive and driven rollers located downstream of the first set just as in the prior device. The second set of rollers rotate at a greater speed than the first set to provide a gap between documents as they are fed. There is an improved lower driven roller design to also use a unique spring which helps hold heavier documents more effectively.
Accordingly, an object of the invention is to provide an envelope feeding device that has an oscillating roller mechanism to aid in separating and feeding envelopes. Related to this is the object of providing an oscillating mechanism which only oscillates when an envelope is not in the feeding nip with the oscillation stopping when an envelope is being fed.
Another object is to provide an envelope feeder which has two sets of feeding rollers with improved separation mechanisms to only permit one document to be fed at a time. Still another object is to provide an envelope feeder which has roller separation means which operate responsive to the thickness of the document being fed to accommodate various size envelopes yet apply the proper force to feed or hold the envelope as desired.
Yet another object is to provide an envelope feeder that feeds the envelopes at an angle that subjects the envelope to minimum bending around the drive roller and allows straight-through envelope feeding.
Many other objects and advantages of the invention will be apparent from the following description of the drawings.